This invention relates generally to the construction of a cargo trailer and more particularly to an improved construction of the side walls of the cargo trailers allowing for a thinner wall construction which results in maximizing the interior volume of the cargo trailer.
There are many cargo trailers and other such containers that typically utilize rectangular panels placed adjacent to each other to form the side walls of the trailers, such as those disclosed in U.S. Pat. Nos. 5,439,266, 4,904,017, 4,810,027 and 6,003,932. The cargo trailers disclosed in those patents typically contain adjacent rectangular plates placed side by side with an additional narrow plate or plates overlapping the adjacent plates to join the plates together.
Wall constructions of this type have been utilized because of the regulations governing such vehicles. These regulations generally limit the overall width of the cargo trailer. The advantage of having the plates side by side with a thin narrow plate(s) to overlap the adjacent panels creates a thin wall that results in a maximum cargo volume. However, because of the size of these panels and the nature of the construction, the structural strength of these side walls is weakened.
The prior art has attempted to construct a thin wall trailer having a maximum cargo volume while maintaining the structural integrity of the walls. Some attempts have been made which eliminate structural posts by increasing the thickness of the panels to increase their integral strength. This results in a much more costly and difficult construction process because of the size of the panels required for these trailers. Other prior art has attempted to integrate the post into the joining plates so that the overall thickness of the wall remains as thin as possible. These wall constructions also have problems. The posts protrude outward of the trailer making them more prone to damage. There are also problems with maintaining the stiffness and structural strength required for the side walls.
The side wall construction of the trailers disclosed in the prior art have additional drawbacks. When these cargo trailers are loaded with cargo, typically a forklift is used to place the cargo in the trailer. Many times the forklift, while doing this, will hit the sides of the trailer causing damage to the sides of the trailer. Eventually, the damage becomes so extensive that the walls have to be replaced, resulting in demotion and reconstruction of the trailer which is very costly.
Additionally, the prior art has constructed thin walls with liners that are made of plastic that snap in between the posts of the wall. These liners, while protecting the side wall, offered no protection of the posts themselves. Other previous cargo trailers have been constructed with plywood liners to protect the posts. However, these plywood liners greatly reduce the interior volume of the trailer and reduce the amount of cargo that can be carried.
Some prior art cargo trailers have front walls constructed of posts with an offset at the front frame so that the outer sheet of the front wall overlaps the front frame like a shingle for weather resistance but the front wall thickness and strength was not a problem.
Thus, there is a need for a cargo trailer side wall that is as thin as possible while still maintaining its structural strength and stiffness. There is also a need for a thin wall construction, which protects the wall posts while still maintaining as thin a wall as possible in order to maximize the cargo volume of the trailer.
The present invention provides an improved construction of a thin wall for a cargo trailer that maintains is structural strength while at the same time protects the posts from damage. More specifically, the thin wall construction consists of adjacent overlapping outer plates, a plurality of regularly spaced thin posts and a plurality of liner panels between the thin posts.
The thin vertical posts are generally hat-shaped (a modified u-shape) in cross-section and are preferably spaced about two feet on center. The posts also coincide with the overlapping joint between the adjacent outer plates. The thin posts contain flanges (the brim of the hat shape) in which there are holes of equal diameter regularly spaced along the length of the flange. The outer plates also contain holes of equal diameter regularly spaced along the outer plates that coincide with the location of the holes in the flanges of the thin posts.
The liner panels are generally a more elongated hat or u-shape in cross-section and also contain flanges along each edge. The flanges also contain holes along their length. The holes along the length of the flange can either be of alternating diameter such that every other hole is of a smaller diameter than the other intermediate hole or can be of equal diameter. The horizontal distance between the two rows of holes in the liner panels is preferably shorter than the horizontal distance between the two rows of holes in the outer plates.
Fasteners are used to connect the liner panels and thin posts to the adjacent outer plates. These fasteners, preferably rivets, are also used to join the adjacent outer plates together in the overlapping area of the plates.
The liner panels as they are connected to the posts and outer panels are stretched because the horizontal distance between the rows of holes in the liner panels is shorter than the horizontal distance between the rows of holes in the outer plates. This stretching of the liner panels prevents the liner panels from buckling and maintains a uniform interior distance between the side walls.
When constructed with alternating diameter holes along the flange of the liner panels, there is an advantage that is not present in other trailer constructions. Because the larger diameter holes are such that they are larger than the diameter of the rivet head, the rivets only engage the liner panel at every other hole in the flange. The advantage of this becomes apparent when the liner panel becomes damaged and needs to be replaced. Unlike other trailers where that entire damaged wall portion would need to be disassembled by removing all of the rivets, in the present invention only the engaging rivets are drilled out leaving the non-engaging rivets intact. The liner can then be replaced without having to disassemble and/or replace the entire wall of the trailer, thereby saving considerable time and cost in repairing the trailer.
The wall construction, however, can also have liner panels containing holes of equal diameter along the length of the flange. The liner panel thus is simpler to construct but still maintains the advantage of the thin wall construction while losing the advantage of the easy replacement of the liner panel.
Additionally, because the liner panels overlap the post flanges, the panels help to protect the post. The overlap forms a ramp which prevents cargo containers and forklifts from catching the post when the cargo is placed in the trailer resulting in less damage to the posts.
A further object of the present invention is to provide the thin posts with a thinner, offset portion at the bottom end to fit inside the bottom rail of the trailer so that the outer surface of the post above that offset portion is substantially planar with the outside of the bottom rail for mounting the outer plate on the post and rail which, in effect, moves the inside of the post outwardly by the thickness of the rail and increases the interior width of the trailer by twice that amount. Preferably, the top end of the posts may be similarly offset to fit inside the top rail with the outer plate mounted therebetween for improved waterproofing while maximizing the internal width of the trailer.
Additionally, a flat stress plate may be provided along a lower portion of the post at or near the bottom offset for increasing the post strength without significantly increasing the side wall thickness.